U.S. patent application number 17/588176 was filed with the patent office on 2022-07-14 for through the wall tank level measurement with telemetry and millimeter wave radar.
The applicant listed for this patent is Lasso Technologies, LLC. Invention is credited to Peter E. McCormick.
Application Number | 20220221322 17/588176 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-14 |
United States Patent
Application |
20220221322 |
Kind Code |
A1 |
McCormick; Peter E. |
July 14, 2022 |
Through the Wall Tank Level Measurement with Telemetry and
Millimeter Wave Radar
Abstract
Methods and systems for determining fluid levels in a tank
comprise a mmWave control unit configured to generate and transmit
a millimeter wave chirp. The control unit transmits the chirp into
the tank through a Luneburg lens and receives one or more chirp
reflections from the tank. For each tank level reading, three or
more chirp configuration profiles are used in order to ensure
accurate depth measurements due to multi-path reflections in most
tanks. The control unit mixes the chirps with the chirp reflections
to generate a set of responses for each chirp configuration
profile. The responses are compared and the two best responses are
selected and averaged. The set of averaged responses are then
processed using a ballot and vote process to determine the distance
reading that is likely to provide the most accurate tank level.
Inventors: |
McCormick; Peter E.;
(Dallas, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lasso Technologies, LLC |
Dallas |
TX |
US |
|
|
Appl. No.: |
17/588176 |
Filed: |
January 28, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16382019 |
Apr 11, 2019 |
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17588176 |
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63142890 |
Jan 28, 2021 |
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62691139 |
Jun 28, 2018 |
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62656032 |
Apr 11, 2018 |
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International
Class: |
G01F 23/284 20060101
G01F023/284; G01S 7/35 20060101 G01S007/35; G01S 7/00 20060101
G01S007/00; G01S 13/34 20060101 G01S013/34; H01Q 15/08 20060101
H01Q015/08; H04W 4/38 20060101 H04W004/38 |
Claims
1. A tank level monitor for measuring a distance from near a top of
a tank to one or more fluids in the tank, comprising: a chirp
generator operable to generate a millimeter wave chirp that ramps
linearly from a starting frequency to a predefined higher frequency
within a specified time span; an antenna and quadrature hybrid
circuit configured to transmit the chirp generated by the chirp
generator into the tank and to receive one or more chirp
reflections from the tank; a Luneburg lens coupled to the antenna
and quadrature hybrid circuit, the antenna and quadrature hybrid
circuit configured to transmit the chirp and receive the chirp
reflections through the Luneburg lens; a mixer operable to mix the
chirp with the chirp reflections to generate one or more
intermediate frequency signals; a processor operable to process the
one or more intermediate frequency signals and derive signal
strengths and distances from the one or more intermediate frequency
signals, each distance indicative of a distance from near a top of
the tank to one of the one or more fluids in the tank or an
obstruction in the tank; and a controller operable to automatically
select intermediate frequency signals having signal strengths above
a predefined minimum or distances within a predefined distance
window for further processing and ignore other intermediate
frequency signals and distances.
2. The tank level monitor according to claim 1, wherein the
controller is programmed to automatically select an intermediate
frequency signal for further processing, the intermediate frequency
signal representing a best returned signal for further
processing.
3. The tank level monitor according to claim 2, wherein the
controller is programmed to automatically further process the
selected intermediate frequency signal by adding the selected
intermediate frequency signal to a ballot, the ballot including
previously selected intermediate frequency signals, the controller
further programmed to automatically vote on the intermediate
frequency signals on the ballot.
4. The tank level monitor according to claim 1, wherein the
controller is programmed to automatically use distance windows to
ignore distances indicative of obstructions in the tank.
5. The tank level monitor according to claim 1, wherein the
controller is programmed to automatically focus on specific
distance windows indicative of fluids in the tank.
6. The tank level monitor according to claim 1, wherein the
processor is operable to process the one or more intermediate
frequency signals using zoom Fourier transform.
7. The tank level monitor according to claim 1, further comprising
a telemetry unit operable to transmit distance readings to an
off-site location.
8. The tank level monitor according to claim 7, wherein the
telemetry unit is configured to use one of the following wireless
telemetry technologies: cellular, satellite, Bluetooth, Wi-Fi,
Z-Wave, ZigBee, WiMax, Sigbox, LoRa, Ingenu.
9. The tank level monitor according to claim 1, wherein the chirp
generator generates a chirp according to a preselected chirp
configuration profile, and wherein the chirp generator is operable
to use three chirp profiles for a given tank level and volume
reading.
10. The tank level monitor according to claim 1, further comprising
a wake button that allows a user to wake the tank level monitor,
the tank level monitor configured to obtain a tank level and volume
reading and to show the reading upon being woken.
11. The tank level monitor according to claim 1 wherein the tank
level monitor automatically wakes as needed to obtain a GPS
location, obtain a tank level reading, and send data representing
the GPS location and the tank level reading wirelessly to an
off-site location.
12. The tank level monitor according to claim 1, wherein the
controller is operable to wake upon receiving a wake command from a
smartphone or a remote display via Bluetooth, obtain a tank level
reading, and send data representing the tank level reading
wirelessly to an off-site location.
13. The tank level monitor according to claim 1, wherein the chirp
generator generates more than 30 chirps per frame sample.
14. The tank level monitor according to claim 1, wherein the
processor is further operable to apply one or more of the following
filters to the intermediate frequency signals: OS-CFAR filter, and
Blackman filter.
15. The tank level monitor according to claim 1, wherein the
controller is further operable to transmit tank level and volume
readings to an external display using Bluetooth.
16. The tank level monitor according to claim 1, wherein the
controller is further operable to transmit tank level and volume
readings to a smartphone using Bluetooth
17. The tank level monitor according to claim 1, wherein the
controller is further operable to receive commands and tank
parameters from a smartphone via Bluetooth.
18. The tank level monitor according to claim 17, wherein the tank
level monitor can receive a tank template from the smartphone, the
tank template containing setup and configuration parameters for a
specific type of tank.
19. The tank level monitor according to claim 1, wherein the
controller is further operable to wake up upon receiving a wake-up
sequence from a smartphone over Bluetooth, the wake up sequence
initiated on the smartphone by a user touching any monitor serial
number via a smartphone app running thereon, the controller further
operable to obtain and send tank level and other tank data to the
user via the smartphone.
20. A method of monitoring tank level for measuring a distance from
near a top of a tank to one or more fluids in the tank, comprising:
generating, at a chirp generator, a millimeter wave chirp that
ramps linearly from a starting frequency to a predefined higher
frequency within a specified time span; transmitting, through a
quadrature hybrid circuit to an antenna, then through a Luneburg
lens, the chirp generated by the chirp generator into the tank;
receiving, through the Luneburg lens coupled to the antenna and
through the quadrature hybrid circuit, one or more chirp
reflections from the tank; mixing, at a mixer, the chirp with the
chirp reflections to generate one or more intermediate frequency
signals; processing, at a processor, the one or more intermediate
frequency signals and deriving signal strengths and distances from
the one or more intermediate frequency signals, each distance
indicative of a distance from near a top of the tank to one of the
one or more fluids in the tank or an obstruction in the tank; and
automatically selecting, at a controller, intermediate frequency
signals having signal strengths above a predefined minimum or
distances within a predefined distance window for further
processing and ignoring other intermediate frequency signals and
distances.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application for patent claims the benefit of priority
to U.S. Provisional Application No. 63/142,890, entitled "Through
the Wall Tank Level Measurement with Telemetry and Millimeter Wave
Radar," filed Jan. 28, 2021, and is a continuation-in-part of U.S.
Non-Provisional application Ser. No. 16/382,019, entitled "Tank
Multi-Level Measurement Using through the Air Millimeter Wave
Radar," filed Apr. 11, 2019, which claims the benefit of priority
to U.S. Provisional Application No. 62/656,032, entitled "Tank
Multi-Level Measurement Using Through the Air Millimeter Wave
Radar," filed Apr. 11, 2018, and U.S. Provisional Application No.
62/691,139, entitled "Tank Multi-Level Measurement Using Through
the Air Millimeter Wave Radar," filed Jun. 28, 2018, all of which
are incorporated herein by reference.
TECHNICAL FIELD
[0002] Embodiments of the invention relate generally to the use of
radar to measure levels of fluids and other materials in a storage
tank and, more specifically, to a self-contained, easy to install,
tank level monitor with integrated display, keypad, radar, GPS, and
cellular and satellite transmission capabilities for sending the
data off-site for further analysis.
BACKGROUND
[0003] Storage tanks are used to store many types of liquids, such
as oil, water, liquid fuels, liquid chemicals, and the like. It is
important in many applications to be able to accurately measure the
level of such fluids in a storage tank, for example, to detect loss
due to leakage and/or theft, for automatic customer billing based
on usage, and also to ensure a sufficient quantity of such fluids
is available. From the fluid level, the volume of fluid in the tank
can be determined using techniques known in the art (e.g., tank
area times fluid level for a circular tank). Measuring a storage
tank's fluid levels typically requires matching the liquid being
stored with a particular sensing technology in order to accurately
determine fluid level. Chemical attributes, viscosity, pressure,
temperature, environment, cost constraints, power-on time, power
requirements, accuracy requirements, and other considerations may
dictate what type of sensor can be used for a given liquid. This is
made even more difficult when the tank contains multiple types of
fluids with different attributes.
[0004] Tank fluid levels are typically read using a mechanical
float on a magneto restrictive rod, or using ultrasonics,
hydrostatic pressure, guided wave radar and pulse radar. These
sensors report data to a remote telemetry modem where the data is
sent, for example, to a web site or other end user. However,
creating a narrow beam width with limited power to pass FCC
requirements and still accurately measure tank levels remains a
challenge.
[0005] Accordingly, advancements are continually needed in the art
of measuring storage tank levels.
SUMMARY OF THE DISCLOSED EMBODIMENTS
[0006] Embodiments of the invention relate to a fluid level monitor
that use a millimeter wave (mmWave) radar system to measure levels
of fluids and other materials in a storage tank. The mmWave radar
system emits a chirp signal that reflects off objects and fluids
and a return signal that is received by a receiving antenna. The
received signal is mixed with the outgoing signal to generate a
signal having an intermediate frequency which is directly
proportional to the distance to one or more levels of fluid in the
tank or obstructions. The fluid level monitor filters out signals
resulting from extraneous obstructions and false signals by
ignoring some resulting distances and lower power signals to
determine the desired distance.
[0007] Advanced algorithms and filters are used to better determine
the true tank level resulting from the monitor's operation. Once
accurately determined, the tank levels and volume are displayed
locally to the user on a display. In addition, wireless telemetry
is used to send the resulting tank levels to remote web sites where
further GPS location, charts, graphs, Key Performance Indicators,
alerts, auto billing, emails, and text messages can be generated
for the end users. In addition to the data being available on the
web, Bluetooth is used to transmit data to a local display or
smartphone. A smartphone can be used to wake and remotely read any
tank's attributes and even program and configure the tank monitor.
The tank monitor is adaptable to plastic tanks but can also be
installed on metal tanks using an adapter. Since the monitor is
totally enclosed, there is no contact with the fluid and the radar
based monitor works on virtually any kind of chemical.
[0008] In general, in one aspect, embodiments of the present
disclosure relate to a tank level monitor for measuring a distance
from near a top of a tank to one or more fluids in the tank. The
tank level monitor comprises, among other things, a chirp generator
operable to generate a millimeter wave chirp that ramps linearly
from a starting frequency to a predefined higher frequency within a
specified time span. The tank level monitor also comprises an
antenna and quadrature hybrid circuit configured to transmit the
chirp generated by the chirp generator into the tank and to receive
one or more chirp reflections from the tank. The tank level monitor
further comprises a Luneburg lens coupled to the antenna and
quadrature hybrid circuit, the antenna and quadrature hybrid
circuit configured to transmit the chirp and receive the chirp
reflections through the Luneburg lens. The tank level monitor still
further comprises a mixer operable to mix the chirp with the chirp
reflections to generate one or more intermediate frequency signals,
and a processor operable to process the one or more intermediate
frequency signals and derive signal strengths and distances from
the one or more intermediate frequency signals, each distance
indicative of the distance from near a top of the tank to one of
the one or more fluids in the tank or an obstruction in the tank.
The tank level monitor yet further comprises a controller operable
to automatically select intermediate frequency signals having
signal strengths above a predefined minimum or distances within a
predefined distance window for further processing and ignore other
intermediate frequency signals and distances.
[0009] In some embodiments, the controller is programmed to
automatically select an intermediate frequency signal for further
processing, the intermediate frequency signal representing the best
returned signal for further processing.
[0010] In some embodiments, the controller is programmed to
automatically further process the selected intermediate frequency
signal by adding the selected intermediate frequency signal to a
ballot, the ballot including previously selected intermediate
frequency signals, the controller further programmed to
automatically vote on the intermediate frequency signals on the
ballot.
[0011] In some embodiments, the controller is programmed to
automatically use distance windows to ignore distances indicative
of obstructions in the tank.
[0012] In some embodiments, the controller is programmed to
automatically focus on specific distance windows indicative of
fluids in the tank.
[0013] In some embodiments, the processor is operable to process
the one or more intermediate frequency signals using zoom Fourier
transform.
[0014] In some embodiments, the tank level monitor further
comprises a telemetry unit operable to transmit distance readings
to an off-site location. In some embodiments, the telemetry unit is
configured to use one of the following wireless telemetry
technologies: cellular, satellite, Bluetooth, Wi-Fi, Z-Wave,
ZigBee, WiMax, Sigbox, LoRa, Ingenu.
[0015] In some embodiments, the chirp generator generates a chirp
according to a preselected chirp configuration profile, and wherein
the chirp generator is operable to use three chirp profiles for a
given tank level and volume reading.
[0016] In some embodiments, the tank level monitor further
comprises a wake button that allows a user to wake the tank level
monitor, the tank level monitor configured to obtain a tank level
and volume reading and to present the reading upon being woken.
[0017] In some embodiments, the tank level monitor automatically
wakes as needed to obtain a GPS location, obtain a tank level
reading, and send data representing the GPS location and the tank
level reading wirelessly to an off-site location.
[0018] In some embodiments, the controller is operable to wake upon
receiving a wake command from a smartphone or a remote display via
Bluetooth, obtain a tank level reading, and send data representing
the tank level reading wirelessly to an off-site location.
[0019] In some embodiments, the chirp generator generates more than
30 chirps per frame sample.
[0020] In some embodiments, the processor is further operable to
apply one or more of the following filters to the intermediate
frequency signals: OS-CFAR filter, and Blackman filter.
[0021] In some embodiments, the controller is further operable to
transmit tank level and volume readings to an external display
using Bluetooth.
[0022] In some embodiments, the controller is further operable to
transmit tank level and volume readings to a smartphone using
Bluetooth
[0023] In some embodiments, the controller is further operable to
receive commands and tank parameters from a smartphone via
Bluetooth. In some embodiments, the tank level monitor can receive
a tank template from the smartphone, the tank template containing
setup and configuration parameters for a specific type of tank.
[0024] In some embodiments, the controller is further operable to
wake up upon receiving a wake-up sequence from a smartphone over
Bluetooth, the wake up sequence initiated on the smartphone by a
user touching any monitor serial number via a smartphone app
running thereon, the controller further operable to obtain and send
tank level and other tank data to the user via the smartphone.
[0025] In general, in another aspect, embodiments of the present
disclosure relate to a method of monitoring tank level for
measuring a distance from near a top of a tank to one or more
fluids in the tank. The method comprises, among other things,
generating, at a chirp generator, a millimeter wave chirp that
ramps linearly from a starting frequency to a predefined higher
frequency within a specified time span, and transmitting, through a
quadrature hybrid circuit to an antenna, then through a Luneburg
lens, the chirp generated by the chirp generator into the tank. The
method also comprises receiving, through the Luneburg lens coupled
to the antenna and through the quadrature hybrid circuit, one or
more chirp reflections from the tank, and mixing, at a mixer, the
chirp with the chirp reflections to generate one or more
intermediate frequency signals. The method further comprises
processing, at a processor, the one or more intermediate frequency
signals and derive strengths and distances from the one or more
intermediate frequency signals, each distance indicative of a
distance from near a top of the tank to one of the one or more
fluids in the tank or an obstruction in the tank. The method still
further comprises automatically selecting, at a controller,
intermediate frequency signals having signal strengths above a
predefined minimum or distances within a predefined distance window
for further processing and ignoring other intermediate frequency
signals and distances.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee.
[0027] The foregoing and other advantages of the disclosed
embodiments will become apparent upon reading the following
detailed description and upon reference to the drawings,
wherein:
[0028] FIG. 1 is an external view showing an exemplary tank level
monitor according to an embodiment of this disclosure;
[0029] FIG. 2 is an interior view of an exemplary a tank level
monitor according to an embodiment of this disclosure;
[0030] FIG. 3 is a schematic diagram for an exemplary tank level
monitor according to an embodiment of this disclosure;
[0031] FIGS. 4A-4C are flow diagrams for an exemplary tank level
monitor according to an embodiment of this disclosure;
[0032] FIGS. 5A-5B are interior views showing a radar board for an
exemplary a tank level monitor according to an embodiment of this
disclosure;
[0033] FIGS. 6A-6C are schematic diagrams for a Luneburg lens used
in an exemplary tank level monitor according to an embodiment of
this disclosure;
[0034] FIGS. 7A-7D are interior views showing a radar assembly for
an exemplary tank level monitor according to an embodiment of this
disclosure;
[0035] FIGS. 8A-8B are views showing a radar assembly housing for
an exemplary tank level monitor according to an embodiment of this
disclosure;
[0036] FIG. 9 is a bottom view of the radar assembly housing for an
exemplary tank level monitor according to an embodiment of this
disclosure;
[0037] FIG. 10 shows front and back views of a radar board for an
exemplary tank level monitor according to an embodiment of this
disclosure;
[0038] FIGS. 11A-11C are schematic diagrams showing a quadrature
hybrid circuit for an exemplary tank level monitor according to an
embodiment of this disclosure;
[0039] FIGS. 12A-12B are circuit diagrams showing operation a
quadrature hybrid circuit for an exemplary tank level monitor
according to an embodiment of this disclosure;
[0040] FIGS. 13A-13B show exemplary chirp profiles for an exemplary
tank level monitor according to an embodiment of this
disclosure;
[0041] FIGS. 14A-14D are graphs of exemplary chirp profiles for an
exemplary tank level monitor according to an embodiment of this
disclosure;
[0042] FIG. 15 shows exemplary status and error messages for an
exemplary tank level monitor according to an embodiment of this
disclosure;
[0043] FIG. 16 shows an exemplary keypad and commands for an
exemplary tank level monitor according to an embodiment of this
disclosure;
[0044] FIGS. 17A-17C are exterior views showing an exemplary tank
level monitor mounted on a tank according to an embodiment of this
disclosure;
[0045] FIGS. 18A-18E are additional exterior views showing an
exemplary tank level monitor mounted on tanks according to an
embodiment of this disclosure;
[0046] FIGS. 19A-19D are still additional exterior views showing an
exemplary tank level monitor mounted on tanks according to an
embodiment of this disclosure;
[0047] FIG. 20 is an exterior view showing an overhead display for
an exemplary tank level monitor mounted on tanks according to an
embodiment of this disclosure;
[0048] FIGS. 21A-21B show a remote display and an iPhone display
for an exemplary tank level monitor according to an embodiment of
this disclosure;
[0049] FIGS. 22A-22C are exemplary smartphone screens for tracking
the location of an exemplary tank level monitor according to an
embodiment of this disclosure;
[0050] FIGS. 23A-23B are exemplary smartphone screens for
monitoring multiple exemplary tank level monitors according to an
embodiment of this disclosure;
[0051] FIGS. 24A-24B are exemplary smartphone screens for reviewing
past tank level volume readings for an exemplary tank level monitor
according to an embodiment of this disclosure;
[0052] FIG. 25 is an exemplary smartphone screen for issuing simple
text commands to an exemplary tank level monitor according to an
embodiment of this disclosure; and
[0053] FIG. 26 show exemplary requests that can be made via a
smartphone app to an exemplary tank level monitor according to an
embodiment of this disclosure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0054] As an initial matter, it will be appreciated that the
development of an actual, real commercial application incorporating
aspects of the disclosed embodiments will require many
implementation specific decisions to achieve a commercial
embodiment. Such implementation specific decisions may include, and
likely are not limited to, compliance with system related, business
related, government related and other constraints, which may vary
by specific implementation, location and from time to time. While a
developer's efforts might be considered complex and time consuming,
such efforts would nevertheless be a routine undertaking for those
of skill in this art having the benefit of this disclosure.
[0055] It should also be understood that the embodiments disclosed
and taught herein are susceptible to numerous and various
modifications and alternative forms. Thus, the use of a singular
term, such as, but not limited to, "a" and the like, is not
intended as limiting of the number of items. Similarly, any
relational terms, such as, but not limited to, "top," "bottom,"
"left," "right," "upper," "lower," "down," "up," "side," and the
like, used in the written description are for clarity in specific
reference to the drawings and are not intended to limit the scope
of the invention.
[0056] This disclosure is not limited in its application to the
details of construction and the arrangement of components set forth
in the following descriptions or illustrated by the drawings. The
disclosure is capable of other embodiments and of being practiced
or of being carried out in various ways. Also, the phraseology and
terminology used herein is for the purpose of descriptions and
should not be regarded as limiting. The use of "including,"
"comprising," "having," "containing," "involving," and variations
herein, are meant to be open-ended, i.e., "including but not
limited to."
[0057] Embodiments of the fluid level monitor herein employ a
single-chip sensor having mmWave measurement capability, such as
one of the family of mmWave sensors from Texas Instruments (TI).
The sensor preferably uses Frequency-Modulated Continuous Wave
(FMCW) radar operating in the 76-81 GHz band with a 4 GHz chirp. An
ARM processor is used for the receivers to control and calibrate
the signals. A built-in Digital Signal Processor (DSP) is used to
perform radar math and run Fast Fourier transforms, such as Zoom
Fast Fourier transform, on the signals to directly determine
distances to fluids. One or more embodiments use a single receive
and transmit antenna and a Luneburg lens configuration to focus the
radar beam. Radar circuits such as the TI mmWave family of
integrated circuits provide compact methods of processing the
necessary signals to determine distance.
[0058] The variations among the TI mmWave family (AWR1443, AWR1642,
IWR1642, IW1843) have different attributes depending upon needs,
but the technology used is the same. One or more embodiments use
the IWR1642 or AWR1642 sensors from TI. The "A" indicates
automotive use, typically for driverless cars, and the "I"
indicates industrial use, but the functionality is otherwise
identical. Examples of fluid level monitors that use one of the
AWR1642 sensors in a manner similar to the embodiments described
herein are available from Lasso Technologies LLC, of Dallas,
Tex.
[0059] Referring now to FIG. 1, a tank level monitor is shown
generally at 100 according to some embodiments. The tank level
monitor 100 is designed to use a mmWave radar that meets FCC
requirements. By way of context, any RF power transmitted in the
United States requires FCC approval and licenses. Different
sections of the FCC code must be passed to be legally used for a
particular application and frequency. The main section dealing with
the use of radar on storage tanks is FCC 15.256 Level Probing Radar
75-85 GHz. The key FCC 15.256 requirements are set out below.
[0060] Fundamental emission limits EIRP 1 MHz and 50 MHz bandwidth
[0061] On tank, pointing down [0062] Stationary use [0063] Peak
EIRP (Equivalent Isotropic Radiated Power) 34 dBm [0064] Azimuth
beam width -3 dB beam width<8 degrees [0065] Antenna side lobe
gain relative to main beam -38 dB
[0066] The tank level monitor 100 disclosed herein can pass the
above FCC 15.256 requirements. In addition, the tank level monitor
100 can be used on smaller tanks 101, such as IBC (Intermediate
Bulk Containers), as well as on virtually any plastic tank or metal
tank when an adapter is used. The tank level monitor 100 has an
advantage of very fast and easy installation, such as by using tape
or adhesive between the radar 102 and the plastic tank wall 105. No
holes need to be drilled in the tank and embodiments of the tank
level monitor 100 can be installed in a few minutes. The customer
can screw or strap the enclosure to the tank if preferred over 3M
tape.
[0067] Embodiments of the tank level monitor 100 can be placed
almost anywhere on top of the tank 101. Packaging the tank level
monitor 100 in an appropriate plastic enclosure allows the tank
level monitor 100 to be used through the access ports on larger
metal tanks, such as an ISO tank. In contrast, alternative
technologies require that a sensor be installed through the tank
wall, which has the disadvantage of needing modifications to the
tank, thus risking damage, direct contact with the fluid, increased
installation time, and potential sensor cleaning issues. The tank
level monitor 100 is also low profile so that the tanks can be
stacked using a forklift, which is not practical with other tank
level measurement methods with higher profile. Display 103 allows
the user to see level and volume in the tank. Embodiments of the
tank level monitor 100 is fully self-contained with integrated
measurement, power, display, and telemetry with no external
antennas, for a clean, easy to install superior solution.
[0068] FIG. 2 shows the tank level monitor 100 with the top cover
removed. As can be seen, the tank level monitor 100 is comprised of
a main control board 202, on which a controller resides that
controls a display, programming keys, telemetry, and transmission
and reception of radar to read tank levels. Housing 201 contains
the radar board and lens which is connected to the main control
board 202 through a power and signal cable 208. Display 205
provides the user with system status, programmability, errors,
level, and number of gallons. Power section 210 provides power to
different sections of the control board 202 as needed. Programming
buttons 204 allow the adjustment of many radar and telemetry
parameters. On/Off switch 207 or magnetic switch 211 can be used to
turn the tank level monitor 100 on using an external magnet to wake
main control board 202. Pushbutton 206 allows a user to wake the
tank level monitor 100 anytime to take a radar tank reading and
display number of gallons and depth on display 205 so the user can
know the tank level. Main control board 202 supervises the
coordination of the various components of the tank level monitor
100. Satellite modem 203 sends data off-site, for example, to web
sites where further data analysis is performed and data is conveyed
to remote users. In place of satellite modem 203, a cellular modem
can be used, or any wireless communication method to send the data.
GPS antenna 209 is used to provide location data so that the
location of the tank level monitor 100 can be embedded with the
tank level information.
[0069] FIG. 3 shows a functional block diagram 300 for the tank
level monitor 100. The functional block diagram 300 contains
controller 302 which pulls data from radar module 309 and controls
other functions of the tank level monitor 100. Controller 302 also
is responsible for controlling the power supplied to radar module
309. Radar module 309 automatically boots up and runs one or more
configuration profiles to determine multiple distances to the fluid
and associated signal strengths. Power is provided using any
suitable non-rechargeable battery 312, or a rechargeable battery
can be used with battery charger 311, or solar panel 310. Power
supply 315 is managed by controller 302 and turned on and off as
needed to each major section of the monitor 100 to save battery
life.
[0070] Controller 302 wakes at intermediate intervals and
communicates with other parts of the tank level monitor 100 to take
level measurements and send them to the user. After taking
measurements, controller 302 puts the tank level monitor 100 in a
low power sleep mode to save battery life. Controller 302 will then
wake as needed and turn on relevant onboard circuits to repeat the
measurement and reporting cycle. Telemetry to off-site locations,
such as external web servers, is provided using a cellular module
306 or satellite telemetry module 307. Other wireless technologies
such as Bluetooth, Wi-Fi, Z-Wave, ZigBee, WiMax, Sigbox, LoRa, and
Ingenu could be implemented for the telemetry module 307 to send
data to an end user. In some embodiments, the tank level monitor
100 has a LoRa module 325 to allow data to be sent to a local
wireless mesh network near the tank. A LoRa antenna 326 can gather
data from similar tank level monitors 100 installed on other nearby
tanks and send the data over wired ground networks or cellular or
other wireless means to web sites, the user, and other
locations.
[0071] The geographical location of the monitor 100 can be
determined using a GPS module 308. In some embodiments, an external
PLC 316 may be used to read data through Modbus circuit 305.
Alternatively, a 4-20 mA transmitter 304 can be used to generate a
4-20 mA signal to PLC 316. Other communication methods to external
ports, such as HART, could also be implemented. Wake early
pushbutton 324 wakes the monitor 100 to take a reading and show the
results on display 318. Bluetooth module 303 is used to communicate
wirelessly with a separate local display 320. A user can press a
button 321 on the local display 320 to read the level and gallons
readings 323 for the tank 352. Bluetooth Low Energy (BLE) is used
so that Bluetooth module 303 can be available when button 321 is
pressed. This is done by using BLE module 303 to wake controller
302 and radar module 309 so that the gallon and level readings 323
are shown to the user. Smartphone 322 and a monitoring app running
thereon can also be used to allow the Bluetooth module 303 to be
used to program setup parameters for the radar module 309 and see
real time updates of the level and volume in the tank, with
interactive charts and graphs, and also to see alarms. In addition,
a smartphone can be used to wake a sleeping monitor 100 by simply
touching any one of the customer's listed devices on their
smartphone. Display 318 or smartphone 322 allows the user to see
the status of the tank level monitor 100, the level, and the
gallons (see FIG. 15), and the programming (see FIG. 16). Keypad
319 allows the user to change the operation of tank level monitor
100, as described in FIG. 16.
[0072] The radar module 309 is an AWR1642 radar chip from Texas
Instruments in some embodiments. The AWR1642 is a single chip that
includes a radar sensor in the 76-81 GHz band with multiple
transmit and receive antennas and built-in phase locked loops (PLL)
and A/D converters. The AWR1642 chip 309 has one cortex R4F core
and one DSP C674x core available for user programming and are
referred to as MSS/R4F 337 and DSS/C674X 336, respectively.
Basically, the MSS processor 337 controls transmission of the radar
signal and the DSS processor 336 processes the received radar
signal using advanced mathematics. Ramp generator 332 works with
synthesizer 333 to generate the chirps, which may be customized via
processor 337. Ramp generator 332 generates a millimeter wave chirp
that ramps linearly from a starting frequency to a predefined
higher frequency within a set time period. In some embodiments,
ramp generator 332 generates more than 30 chirps per frame
sample.
[0073] The tank level monitor 100 configures the chirp generator to
send 64 chirps in some embodiments instead of the more common 10
chirps used in the art. These 64 chirps are averaged, which
minimizes much of the noise and also improves the accuracy of the
final tank level and volume readings. The quadrature hybrid circuit
340 allows the transmit signal from power amplifier 331 to reach
antenna 341 with no feedback to damage the low noise amplifiers
(LNA) 330. The Luneburg lens 342 creates a focused RF signal,
indicated at 353, from antenna 341 towards fluid 351 in tank 352.
The echoed response signal 353 feeds back through the lens 342, and
quadrature hybrid circuit 340 to the receive LNAs 330. Only one
transmit and receive antenna is used on the AWR1642. Mixers 334
receive and multiply the signal being transmitted with the signal
being received that instant from the low noise amplifiers 330 and
antenna 341. The product of the mixers 334 creates the intermediate
frequency (IF) signal 335 which is sent to the analog to digital
converters 336. The digital front end 338 receives the signals and
digitizes and stores these values in analog buffers for use by the
DSP 336. The DSP 336 performs the signal processing of the received
signals and runs a Fast Fourier transform (e.g., Zoom), OS-CFAR,
and Blackman routines on each peak of the IF signal to determine
distances to fluid.
[0074] Processor 337 works with memory 339 to coordinate the
various functions on the radar module 309. A single tank level and
volume reading can be determined within the DSP 336 and used as the
correct distance reading, or the 10 strongest distance readings in
terms of signal power can be sent over serial port 345 to
controller 302 for further analysis. It should of course be
understood that fewer or more than 10 strongest distance readings
may be sent for further analysis by controller 302. Satellite
telemetry module 306 and cellular telemetry module 307 can be used
to transmit data off-site as scheduled or needed. GPS location data
is captured using GPS circuit 308.
[0075] FIG. 4A shows a flowchart 400 outlining the basic steps for
processing a radar echo in the tank level monitor 100 in some
embodiments, while FIG. 4C shows exemplary signal peaks A, B, C, D,
E, F, G, H, I, J generated from an actual radar echo. For most
embodiments, 10 data points will be analyzed corresponding to the
10 strongest peaks resulting from the 64 chirps. Any of these 10
peaks could represent the correct fluid level, since multiple
echoes are usually returned for each chirp due to reflections
within the tank and inherent noise in the radar circuit.
[0076] The flowchart 400 generally begins at 401, where the tank
level monitor 100, or more specifically the radar module 309
therein, sets the current/next radar chirp configuration profile.
At 402, the radar module 309 generates 64 chirps that are
transmitted into the tank. Experience has found that increasing the
chirp width greatly improves the accuracy of the resulting fluid
level readings. Intuitively, increasing the transmitted power would
seem to yield better results, but increasing the transmitted power
actually increases noise and reflections and can produce erroneous
results. Likewise, increasing the received amplification can
degrade performance if over-amplification of noisy echoes produces
bad level readings. Increasing the chirp loops can improve
performance accuracy. Multiple chirp profiles with different
transmitted and received power, chirps, chirp widths, and chirp
loops are used while determining a valid level.
[0077] At 403, the radar module 309 collects data from the return
echoes of the current chirp configuration profile. Three chirp
configuration profiles are contemplated, although fewer or more
than three profiles may certainly be used. The data collected is
the signal strength or power for various reflections or echoes
resulting from the chirp, along with the corresponding range or
distance to the fluid for the reflections based on the signal
strength or power.
[0078] At 404, the radar module 309 makes an initial determination
of the 10 best (strongest) peaks based on the signal strength of
the reflections or echoes, along with their range or distance to
the fluid. Exemplary peaks A, B, C, D, E, F, G, H, I, J are shown
in FIG. 4C. At 405, the radar module 309 runs a Zoom Fast Fourier
Transform (FFT) on each of the 10 best (strongest) peaks, or rather
the digitized representations of their waveforms. The Zoom FFT
determines the spectral components of the peaks in order to
determine the distances to the fluid, since distance is directly
related to the intermediate frequency (IF). To improve resolution,
the radar module 309 uses a Zoom FFT processing technique that
enhances the 10 strongest return signals. This is a processing
technique that is added as an enhancement to the existing chip
software in the DSP 336. Zoom FFT processing of the 10 strongest
return signals allows analysis of the fine spectral resolution of
each peak of the returned data at high "Zoom" resolution. In some
embodiments, the radar module 309 applies the Zoom FFT to each of
the 10 peaks (using the DSP 336) as follows: [0079] Frequency
translation to shift the frequency range to 0 Hz. [0080] Low-pass
filter to prevent aliasing. [0081] Re-sample at a lower rate.
[0082] Perform Zoom FFT on the re-sampled data (the resulting
spectrum will now have a much higher resolution bandwidth, which
results in better distance accuracy).
[0083] The above Zoom FFT process is repeated on each of the 10
example peaks A, B, C, D, E, F, G, H, I, J shown in FIG. 4C,
resulting in a precise IF for each peak that can be translated into
a distance or range to fluid. The result is a set of 10 ranges
corresponding to the 10 peaks, each range having a corresponding
signal power or strength value, for a given chirp profile, as
follows: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE
10th, POWER 10th].
[0084] At 406, the radar module 309 applies a filter to the data
from 404 to eliminate false range or distance readings for each of
the 10 values. This is to account for real-world tanks that often
produce spurious reflections and echoes, potentially resulting in
false distance readings, making detecting the correct distance
challenging. In some embodiments, the filter applied by the radar
module 309 is a mathematical algorithm, such as the well-known
Order Sorted-Constant False Alarm Rate (OS-CFAR) algorithm, to
minimize false readings. Background noise and false reflections can
cause noise problems, so setting an accurate signal strength
threshold for the returned signal is challenging. Setting a
frequency threshold level for all distance readings does not work
since the noise floor varies for different distance readings. The
OS-CFAR algorithm uses a varying threshold based upon the present
noise level, which is independent of the surrounding noise power
for the underlying noise model, as determined by evaluating
neighboring frequencies using a sliding window to inspect all
frequencies. A changing threshold is calculated from the
signal-to-noise ratio of the fluid echo return by estimating the
noise floor near the frequency of interest and calculating the
average power level. A frequency and thus distance is valid if it
exceeds this threshold.
[0085] At 407, the radar module 309 runs additional filtering, for
example, by applying a Blackman filter routine, to the data from
404 to smooth the data. The well-known Blackman filter is effective
for pulling out very small signal levels which are superimposed on
larger signals.
[0086] At 408, the radar module 309 checks whether Zoom FFT,
OC-CFAR, and the Blackman routines have been run on all 10 peaks.
If not, then the radar module 309 continues until all 10 data
points are processed. The resulting 10 ranges and corresponding
signal strengths are then stored for that chirp profile. An
exemplary set of samples or data for a given chirp profile may
resemble the following: [210.9, 60.6] [334.3, 138.7] [459.7, 17.3]
[658.8, 1.0] [824.5, 0.4] [914.2, 0.3] [1007.8, 0.2] [1102.4, 0.2]
[1680.4, 0.2] [1748.4, 0.2] where range is in millimeters (mm) and
power is in decibels (dB), respectively.
[0087] At 409, the radar module 309 checks whether three chirp
configuration profiles have been run as described above, with 10
ranges and corresponding signal strengths stored for each of the
three chirp profiles. This results in three sets of samples or
data, one set for each chirp configuration profile, each set
containing 10 range-power pairs per profile. Each set of data is
sometimes referred to herein as the "response" resulting from a
given chirp profile.
[0088] At 410, each of the three responses are evaluated and the
two responses that have the most similar ranges/distances to one
another are selected. In some embodiments, the evaluation involves
comparing the ranges/distances of the three responses to determine
which two responses line up most closely with one another (i.e.,
have the smallest variations). Several ways exist for performing
the comparison, including comparing individual ranges/distances
within one response to another, averaging the ranges/distances and
comparing the average for one response to another, and the like.
Three exemplary responses are shown below, Res 1, Res 2, and Res
3:
Res 1: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE
10th, POWER 10th]. Res 2: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER
2nd] . . . [RANGE 10th, POWER 10th]. Res 3: [RANGE 1st, POWER 1st]
[RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th].
[0089] Of these three responses, assume that Res 2 and Res 3 have
ranges/distances that are most similar to one another. In that
scenario, Res 2 and Res 3 are selected while the first response,
Res 1, is discarded or otherwise not used. The radar module 309
then averages the range values and the power values for these two
responses, Res 2 and Res 3, to produce a single set of 10
range-power pairs. This approach has been found to consistently
produce the most accurate results.
[0090] At 411, the radar module 309 sends the data for further
analysis by the controller 302. The controller 302 attempts to
select the best range-power pair from among the 10 range-power
pairs. The selected range-power pair is then placed on a "ballot"
along with other (previously selected) range-power pair candidates
and put to a "vote" to determine the best candidate thus far. This
process helps to weed out bad readings that sometimes get
repeated.
[0091] In some embodiments, the controller 302 selects the best
range-power pair from among the 10 range-power pairs by ignoring
distances that are too close to the top of the tank (i.e., signal
strength above a certain decibel level) or too large such that they
extend beyond the bottom of the tank. This may be done by setting
appropriate signal strength or distance thresholds or windows
(i.e., minimum and maximum acceptable signal strength level and
distance level). For example, the signal strength threshold may be
a decibel level representing 10 inches from the fluid to the top of
the tank (i.e., too close to the top), or three inches of fluid
remaining in the tank, or some other decibel level indicating that
the tank is effectively empty. The controller 302 then selects the
remaining range-power pair having the strongest signal as the best
candidate.
[0092] If no strong signal is found, the controller 302 then checks
whether there is a signal with a distance near the bottom of tank,
but still greater than a first threshold representing a depth near
the bottom of the tank (i.e., signal>threshold 1 (roughly 10
dB)). If yes, then the range-power pair for that signal is selected
as the best candidate from the 10 pairs. If still no strong signal
is found, then the controller 302 checks whether the signal is very
weak, less than a second threshold representing an effectively
empty tank (i.e., signal<threshold 2 (roughly 3 dB)). In that
case, the controller 302 puts a range-power pair that represents an
empty tank on the ballot. The thresholds and windows can be set
automatically by the monitor 302 for a given tank, or they can be
set manually by users and revised from time to time as needed.
[0093] The above process allows signals that have a reasonable
strength level, but are not necessarily the strongest signal, to
still be considered in determining a correct distance measurement.
Using a signal strength threshold for echoes that are more distant
means that the echoes with the strongest power value will not
necessarily be used, but this is likely to produce the correct
distance to the fluid. This is because, for example, data for peak
A may indicate a strong echo, but that echo may be due to an
obstruction near the top of the tank and does not represent the
correct distance to the fluid. On the other hand, data for peak B
may represent the correct distance measurement, even though it has
only 80 percent of the maximum signal strength shown by peak A. The
approach taken at 412 thus allows distances that most likely
represent the correct distance to be used instead of using
incorrect distances based on the strongest peaks. The final most
likely depth value candidate is then "voted," as continued in FIG.
4B.
[0094] Referring to FIG. 4B, even though special filtering,
advanced math and other techniques are used to determine the
correct distance to the fluid, spurious random incorrect distances
sometimes are returned by the radar module 309. Additional measures
can be implemented to prevent incorrect readings from being
presented to customers. To this end, a list of the candidate
distances determined by the controller 302 are maintained at 420
during the time period that the radar module 309 is on (e.g., 5
seconds). During this radar on-time, the radar module 309 runs the
three chirp configurations twice per second, resulting in 10 runs.
The controller 302 thus produces 10 best range-power pair
candidates per each 5-second run of the radar module 309. Each of
these 10 range-power pair is potentially a candidate to be voted on
as the correct fluid depth.
[0095] At 421, the controller 302 determines, from the 10 fluid
depths returned by the radar module 309, whether the fluid depth
with the highest signal strength is within a predetermined
variation, such as 0.5 inches or a certain percentage, of the prior
depths. If yes, then that depth (i.e., one with the highest signal
strength) is considered to be already included on the current list
or "ballot" of depths. The flowchart 400 then proceeds to 423 and a
"vote" is cast for that existing best depth. If no, then the depth
is considered to be a new best depth, and the new best depth is
added to the "ballot" at 422. A vote is again cast for the best
depth at 423. The radar module 309 typically stays on for 5 seconds
and reads around 15 depth/distance measurements during that time.
At the end of the 5 seconds, the controller 302 looks for the
depth/distance with the most votes at 424, and that depth is
presented to the user as the "correct" depth/distance at 425. At
426, the controller 302 checks whether the radar module 309 On-time
is done. If not, then the flowchart 400 returns to FIG. 4A and
continues the process. If yes, then at 427, the controller 302
presents the depth/distance with the most votes the user via the
displays and/or the telemetry module.
[0096] Thus, by using multiple chirp configuration profiles,
filtering, and voting as described above, the tank level monitor
100 provides a depth detection method that is extremely reliable
and accurate.
[0097] FIGS. 5A-5B show an exemplary embodiment of the tank level
monitor 100 partially disassembled. As can be seen, the tank level
monitor 100 comprises an enclosure 500, a battery 502 or
rechargeable battery 503, main control board 501, display 505, and
programming buttons 506. The battery can take on many forms, such
as a sealed lead acid battery 502 or Lithium Thionyl Chloride
battery 503. A radar assembly 504 is also shown that sends the
distance measurements to the main control.
[0098] FIGS. 6A-6C show an exemplary horn 600 that may be used in
some embodiments to focus the radar energy on the fluid. As this
cut-away view shows, the horn 600 includes a lens 601 and antenna
arrangement that is used to focus the radar energy on the fluid.
The lens is a Luneburg lens 601, which is a spherically symmetric
(ball shaped) gradient-index lens that can transform the spherical
wave of a point source placed on its surface into plane waves on
the opposite side of the lens. A Luneburg lens' dielectric constant
ideally is 2 at the center 604 and gradually decreases to 1 on the
outer surface 603 to match the dielectric of air. Ideally, the lens
will start from a focal point on one side and parallel radiation on
the opposite side with a focal point of infinity and plane waves.
Within the lens, the paths of the rays are arcs 605. On the
surface, no reflection or bending occurs creating parallel rays
612. Many variations of a Luneburg lens have been developed over
the years. This tank level monitor 100 uses a solid Teflon ball 601
as a lens which has low tangent losses, and a dielectric constant
of about 2.2, which results in a performance similar to an ideal
Luneburg lens at much less cost. Other radar compatible plastics
such as Rexolite, Preperm, or Polyethylene can also be used instead
of Teflon. The RF signal is emitted from antenna 606 through the
waveguide 607 and into the lens 601. Plastic screws 609 support the
ball using drilled dimples. The wave planes pass through cavity 608
and through the enclosure wall 610. The lens focuses the beam into
a tight pattern 620 with minimal side lobes which can pass FCC
requirements for tank level measurement. Several other antennas
tried do not come near this performance.
[0099] FIGS. 7A-7D show different views of the radar assembly 700.
The radar assembly 700 is comprised of a housing 702, the Luneburg
lens cement tree and a radar board 704 which contains the radar,
quadrature hybrid circuit, radar computer, and antenna. Housing 702
contains the radar circuit board 704 and mates with assembly cover
707. Assembly cover 707 may be lined with radar absorbing rubber
708 to help meet FCC radiation requirements. Header 705 is used for
programming and connection to the main control board 302. Luneburg
lens 703 is suspended in the center of the assembly cover 707 using
plastic screws 706 in some embodiments.
[0100] FIGS. 8A-8B show the exemplary radar housing in more detail.
The radar housing or enclosure 800 is generally made of two halves,
and upper half 802 and a lower half 804. Radar absorbing material
806, such as ARC SB-1006, lines the inside of the upper half 802 to
decreases RF side lobes. Plastic screws 808 suspend the Luneburg
lens 803 to provide separation from the housing so the RF power is
not altered, and also holds the two halves together. Waveguide 805
directs the RF energy from the patch antenna (i.e., the metal trace
antenna pattern in the circuit board (see FIG. 7A at 704) to the
Luneburg lens. Threaded holes 807 are provided to screws and secure
the radar board in place. Mounting holes 809 are used to fasten the
upper half to the bottom half of the enclosure 800.
[0101] FIG. 9 shows a further view of the radar assembly at 900.
The radar housing 901 contains the Luneburg lens and the radar
board. Radar chip 907 is one of the mmWave products from TI, in
this case the AWR1642. This powerful radar chip handles the RF
signals necessary to determine distance. Antenna contact 903 feeds
the signals from the patch antennas into waveguide 904. Alignment
posts 906 mate with radar board 902. Pocket 905 provides clearance
for the radar chip 907. Circuit board 902 is the radar board and
has six trace layers and special plating to maximize
performance.
[0102] FIG. 10 shows the radar board 1000 in more detail. The radar
board 1000 has a power section 1007, debug-programming connector or
header 1006, and can interface directly to controller 302.
Quadrature hybrid circuit 1008 with dual antenna feeds is
diagrammatically shown but the actual traces are on an internal
layer within the board. Antenna contact 1001 feeds the Luneburg
lens discussed earlier. Screws-in holes 1002 allow the board to be
anchored to the radar housing. The mmWave radar AWR1642 can be seen
at 1004 and is also represented elsewhere herein by reference
309.
[0103] FIG. 11A shows the circular polarization of the RF energy,
which is the ideal waveform desired to improve the likelihood that
a signal will be reflected. In a circularly polarized antenna, the
plane of polarization rotates in a corkscrew pattern making one
complete revolution during each wavelength. Since circular
polarized antennas send and receive in all planes, the signal
strength stays strong as the signal transfers to a different
plane.
[0104] FIG. 11B shows a schematic diagram of a quadrature hybrid
circuit 1100. The quadrature hybrid circuit 1100 allows the use of
a Luneburg lens with high gain, narrow beam width and a single
antenna used for both the transmitter and receiver. As seen in FIG.
11C, the quadrature hybrid circuit 1100 is basically a power
splitter that divides an input signal 1101 into two outputs 1103
and 1104 having a 90.degree. phase shift therebetween. The transmit
power from the radar chip 1113 (AWR1642) has a 90.degree. phase
difference after passing through the quadrature hybrid circuit
1100, which is connected to the two axes 1103 and 1104 of a
waveguide feeding antenna 1115 to emit circularly polarized waves.
The power of the input signal 1101 is split equally between the
coupled through-ports 1103 and 1104 with a 90.degree. phase
difference. Signal power reflection is prevented from damaging the
Receive (RX) input 1112 of the radar chip 1113 because the coupled
ports are isolated by a resistor on line 1102 from the output ports
1103 and 1104 and due to the nature of a quadrature hybrid circuit.
The RF energy reflected by the tank fluid enters antenna 1115 and
feeds into axes 1103, 1104 and back through the quadrature hybrid
1100. Phase shifts in the quadrature hybrid direct the energy back
over the line 1102 into the receive signal 1112. No power goes back
to the Transmit (TX1) pin 1101 since this is now the isolated port
on the quadrature hybrid. Ground 1110 surrounds the antenna to
maintain 50 ohms impedance matching. The physical dimensions of the
rectangular aperture 1108 in the quadrature hybrid circuit 1100 are
.lamda./4, or about 1 mm by 1 mm at 80 GHz. The impedance of the
quadrature hybrid 1105 Zo is 50 ohms.
[0105] FIGS. 12A-12B graphically illustrates two signals that are
90 degrees apart as applied to two inputs on a patch antenna in the
radar board 1200. This will create a circularly polarized radar
signal. The quadrature hybrid circuit described above, and the
patch antenna are etched onto the radar circuit board 1200. When
the radar chip 1201 transmits, it sends a chirp, indicated that
1203, with a transmit power and phase angle of zero. The quadrature
hybrid circuit 1210 splits this incoming power in half into two
signals 1204 and 1205 at 90 degrees and 180 degrees apart from the
incoming phase. The signals combine in antenna 1208 to create a
circular polarized radar signal. The RF signal from antenna 1208
passes through Luneburg lens 1207, through the air in the tank 1219
and is reflected by the fluid 1220 therein. When the RF signal is
reflected by the fluid, the signal passes through the Luneburg lens
1207 into antenna 1208 and again the signal is split into two half
power signals 1213 and 1214 which are 90 degrees apart. They pass
through the quadrature hybrid 1210. Due to the nature of the
quadrature hybrid, no power is returned to the Transmit (TX) port
and all power goes to the Receive (RX1) port. The Transmit (TX)
port becomes the isolation port for the quadrature hybrid circuit.
Reflections from mismatches sent back to the output ports are
cancelled by the radar chip 1201. The processor and the telemetry
module, both generally indicated 1221, direct the generation of
chirps, data gathering, and determination of the depth level as
described previously.
[0106] FIG. 13A show an example of the radar chirp signal at 1301.
The radar generates this exemplary chirp signal to determine fluid
level in the tank. Measuring fluid level in a tank using mmWave is
challenging because there are many reflections and multiple paths
of the signal between the tank walls. Reflections and excess noise
due to high amplification can cause erroneous readings of the fluid
level. Embodiments of the tank level monitor 100 uses various
methods to improve the accuracy of the tank level and volume
readings.
[0107] FIG. 13B shows a list of different configuration profile
parameters used by the mmWave radar module 309, specifically the
AWR1642 radar chip. These parameters are stored in nonvolatile
memory in the AWR1642 chip and include the gain, number of chirps,
timers, number of samples, and chirp frequencies. The high and low
pass filters can be changed by the user within the AWR1642 radar
chip. In most instances, there is no single set of operational
parameters that suits all fluids and fluid levels. Accordingly, in
some embodiments, an approach of using three or more profiles 1304
to generate chirps in rapid succession and selecting the best
outcome provided an excellent method of obtaining good measurement
results. Some of the chirp parameters that can be changed are shown
at 1303. The software in the AWR1642 radar chip can automatically
generate chirps using three configuration profiles in very rapid
succession and collects data on each resulting response. Data is
analyzed automatically as described previously in FIG. 4 to return
the correct fluid level to the user.
[0108] FIGS. 14A-14D show performance data associated with
different chirp configuration profiles. The data shows the
performance of the radar module as used to measure fluid level
while draining a tank a few inches. The tank depth readings in
these figures show that, although not required, it is beneficial to
run multiple different chirp profiles. Three different chirp
configuration profiles I, II, and III were used in this example, as
shown in graphs 1401, 1402, 1403 in FIGS. 14A-14C. Each chirp
configuration profile resulted in sporadic high and low spikes 1410
in the measurements. These sporadic spikes 1410 are due to
multi-path reflections and noise in the radar system that result in
large measurement errors. As can be seen in graphs 1401, 1402,
1403, the radar module 309 produced different measurement curves
using the three different configuration profiles. This demonstrates
that a single chirp configuration profile will not produce good
measurement results given an unknown fluid level. Running different
configuration profiles and selecting the best results as described
herein provides a more accurate way to determine the correct fluid
level. Radar module 309 can automatically use three different
profile-configurations using processor 337 and can gather the
resulting tank level measurements. Three responses are obtained,
each representing a different configuration profile, and each
containing 10 sets of distances and signal strength
measurements:
Res 1: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE
10th, POWER 10th] Res 2: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER
2nd] . . . [RANGE 10th, POWER 10th] Res 3: [RANGE 1st, POWER 1st]
[RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th]
[0109] Then, two of the three responses from above that have the
strongest signal strengths are then averaged to create a set of 10
best distance and signal readings, as shown at 1404 in FIG. 14D. As
mentioned earlier, this may include, for example, [RANGE 1st, POWER
1st] from profiles 1 and 2, [RANGE 2nd, POWER 2nd] from profiles 2
and 3, [RANGE 10th, POWER 10th] from profiles 1 and 3, and so on.
As this figure show, merging the chirp responses (by ignoring depth
level readings that vary greatly from their counterparts) shows
that running multiple chirp profiles can produce highly accurate
results.
[0110] In general, individual configuration profiles typically have
an error of about 5-10%. The three-configuration profile approach
herein can produce results with an accuracy of within 0.5 percent,
as seen in graph 1404. And the radar module 309 can perform all of
this in about 0.5 seconds. The set of range/distance and signal
power readings is then sent to controller 302 to determine the most
likely correct level using the process described with respect to
FIGS. 4A-14C. A single fluid depth and gallons are then sent to the
user on display 318 and telemetry modules 306 or 307.
[0111] FIG. 15 shows exemplary messages that may be displayed to
the user on display 318 or sent off-site via the telemetry modules
306 or 307. These messages include system status messages, examples
of which are listed at 1501, as well as system error messages,
examples of which are listed at 1502. These messages provide users
with useful information about the tank level monitor 100. Those
having ordinary skill in the art will understand that other status
and error messages besides the ones shown here may also be
used.
[0112] FIG. 16 shows an exemplary keypad 1601 (also see FIG. 3 at
319) that may be used in some embodiments to program operation of
the tank level monitor 100. The programmability of the tank level
monitor 100 allows it to be used in many diverse situations on
different chemicals. An exemplary list of programming messages is
shown at 1602 (along with information about the parameters). These
messages 1602 may be displayed to the user via the display 103 to
assist the user in programming the tank level monitor 100.
[0113] FIGS. 17A-17B show different views of the tank level monitor
100 in isolation and FIG. 17C shows a view of the tank level
monitor 100 as installed on top of a tank. As discussed previously,
the tank level monitor 100 can used on virtually any type of tank.
The typical installation is where the monitor 100 is placed on top
of a plastic tank 101 and the radar signals can "see" through the
plastic tank wall. Installation on metal tanks is also possible by
using a special adapter to mount to one of the tank flanges, as
shown in FIGS. 17A and 17B. An ISO tank with a typical 2-inch NPT
fitting is shown at 1700 in FIG. 17C. In FIGS. 17A and 17B, a
nipple 1703 screws into a tank flange 1705. Teflon plate 1702
screws onto nipple 1703 and the tank level monitor 100 is attached
to the plate 1702 so that the radar beam is centered over the
2-inch nipple. The Teflon plate has a low dielectric constant, so
the radar beam easily passes through it while it inherently
protects the radar from the caustic fluid and seals the tank.
Shut-off valve 1704 keeps fluid from leaking in case there is a
major accident and the tank rolls over during transportation and
breaks plate 1702 from nipple 1703. Many other mounting techniques
are available within the scope of the disclosed embodiments.
[0114] FIG. 18A-18E are views of the tank level monitor 100 mounted
on several different types of tanks. The tank level monitor 100,
with its adaptive algorithms and sophisticated filtering and depth
discernment, can be adapted to many types of tanks. Adapter 1702
from the previous figures can be used for mounting and to access
fluid on larger tanks. Smaller ISO tanks 1803, as well as larger
poly tanks 1801, metal ISO Tanks 1802, ISO tanks 1804, tanks 1805
of the type used in tank farms.
[0115] FIG. 19A-19D are views of the tank level monitor 100 mounted
on taller chemical tanks 1901 where the tank level monitor 100 can
sit unseen at the top of the tank and transmit level readings by
satellite, smartphone or locally to the monitor's remote display.
The tank level monitor 100 can also be mounted on the taller poly
tanks 1902, 1903, as well as frac tanks 1904.
[0116] FIG. 20 shows an embodiment where the tank level monitor 100
(not expressly seen) is used to send fluid level readings for a
tank 2000 to an overhead display 2001. A close-up view of the
overhead display is shown at 2002. Looking at an overhead display
2002 is faster than accessing data online or via a smartphone and
is particularly helpful when taking tank level inventories from a
moving vehicle, such as a pickup truck, or when an operator is
walking through the tank yard. The tank level monitor 100 sits on
top of the tank 2000 and takes measurements of the fluid level,
then transmits data to an overhead display 2002, such as an LCD
display. The LCD display 2002 is preferably a type that continually
displays the data sent to the display and is only updated when new
data is received from the tank level monitor 100. Back lighting
turns on so the LCD display 2002 can be seen at night. The LCD uses
very low current for battery power. In some embodiments, a separate
remote display 2003 can be used to get the current level detailed
readings in the tank.
[0117] FIGS. 21A-21B show examples of the tank level monitor 100
communicating with a remote display 2101 or a smartphone 2111 using
Bluetooth. Remote display 2101 is positioned at the base of a tall
tank, such as the one shown at 2000 (FIG. 20). The operator can
then press button 2102 on the remote display 2101 to get the
current level within seconds. When the button is pressed, a BLE low
power Bluetooth module on the remote display 2101 communicates with
and wakes up the tank level monitor 100. Having a Bluetooth module
in the tank level monitor 100 creates a private wireless serial
connection with the smartphone 2111 or remote display 2101 when a
device requests a connection. When sleeping, the monitor 100
advertises its identity using BLE to interrogate whether a
smartphone or remote display wants to communicate. Monitor 100
takes readings and updates local display 2104 as well as sends data
to the user at the base of the tank on display 2101. Alternatively,
smartphone 2111 can display the current tank status as well as be
used to program the tank level monitor 100. A suitable smartphone
app can use the Bluetooth capability of each monitor 100 to allow
the user to select a specific monitor 100 and create a private
communication link to that monitor 100. Any one of many monitor 100
nearby (within Bluetooth range) can be accessed using a smartphone.
This same Bluetooth capability allows the remote display or
smartphone to access data and wake the monitor from sleep without
touching the monitor 100.
[0118] FIGS. 22A-22C show examples of screens that may be displayed
on an iPhone or Android app for the tank level monitor 100. The
exemplary smartphone screen 2201 in FIG. 22A shows all the various
monitors 100 that belong to a particular login or customer. The
exemplary smartphone screen 2202 in FIG. 22B shows the location of
all monitors 100 on a map. The exemplary smartphone screen 2203 in
FIG. 22C shows driving instructions that can guide the user to the
site. The screens leverage the existing GPS location and navigation
capability equipped in most Smartphones
[0119] FIGS. 23A-23B show examples of screens that may be displayed
on a smartphone to allow a user to select which of several monitors
to evaluate. An additional feature is the ability for the user to
touch any of the serial numbers 2201 on the smartphone to initiate
a wake-up sequence for that particular monitor 100 over Bluetooth.
Within seconds of doing so, the monitor 100 wakes (if sleeping) and
accepts a private connection (i.e., via a handshake) between the
smartphone and that monitor, a tank reading is taken, and the
monitor 100 sends data to the smartphone showing tank level,
battery level, any error messages, distance to fluid, and signal
strength data (see FIG. 24A at 2401). The exemplary smartphone
screen 2301 in FIG. 23A shows all the various monitors 100 that
belong to a particular login or customer account. Once the monitor
is selected as shown in smartphone screen 2305 (e.g., by using drop
down menu 2307), the user can select the date range of interest at
fields 2308 and see all depth readings taken during the selected
date range at 2309.
[0120] FIGS. 24A-24B show examples of screens that may be displayed
on a smartphone to allow a user to directly communicate with a
selected monitor 100. The exemplary smartphone screen 2401 in FIG.
24A shows a smartphone app that uses Bluetooth to allow the user to
directly communicate with a selected monitor 100 and see all
current depth readings taken by the monitor 100. The exemplary
smartphone screen 2402 in FIG. 24B shows a smartphone app that
allows the user to access and see any alarms that may have occurred
at a selected monitor 100.
[0121] FIG. 25 shows an example of a screen that may be displayed
on a smartphone to allow the user to communicate with a selected
monitor 100 using simple text messages. The exemplary smartphone
screen 2501 in FIG. 25 shows a smartphone app that uses Bluetooth
to allow the user to send simple text messages to the selected
monitor 100. The controller 302 in the monitor 100 receives the
text messages via the Bluetooth module 303 and extracts the text
information therefrom. Programming within the monitor 100 processes
the extracted text information and modifies the appropriate
operational parameters stored in the controller 302 accordingly. To
this end, the text information needs to be in a format that is
understandable and recognizable by the controller 302. Examples of
text messages that may be sent to the monitor 100 are shown at 2502
and can include parameter values that can be directly downloaded
into the monitor from the text messages. Commands may be sent to
the monitor 100 from a smartphone via Bluetooth in a similar
manner.
[0122] FIG. 26 shows examples of commands that a user may send to
the monitor 100 via a smartphone to allow the user to control
various operations. The exemplary commands, indicated at 2601,
allow the monitor 100 to be programmed using the smartphone. In
some cases, the user can also use the smartphone to request a
current tank parameter, indicated at 2602, for a given tank. The
monitor 100 also has tank templates 2603 saved therein for various
types of tanks to allow the user to quickly configure the tank for
customer's monitor. The tank templates include various attributes
about the tanks that the user may fill in via the smartphone. These
attributes may include a lookup strapping chart for the customer's
tank, radar power needed for the tank, tuning settings for the
tank, distance at top of tank (to ignore for reading purposes),
tank height, other tank dimensions, time of day call-in times, GPS
update times, and even GMT time offset in some cases. The tank and
radar settings and other information may be stored on the
smartphone in some embodiments, or the information may be stored on
the monitor 100 in some embodiments, or a combination of both. In
embodiments where the tank templates and information are already
preloaded on the monitor 100 (which is normally the case), a
customer may simply send a command like "T12" (see 2603) to
automatically configure a particular tank. This speeds installation
of the monitor 100 on the tank, particularly when all tanks in a
large tank yard are identical, so manual tuning of the monitor is
not required.
[0123] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments will be apparent to those
skilled in the art. The various aspects and embodiments disclosed
herein are for purposes of illustration and are not intended to be
limiting, with the true scope being indicated by the following
claims, along with the full scope of equivalents to which such
claims are entitled.
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